Electrostatic ionic air emission device

ABSTRACT

The invention concerns an electrostatic ionic emission device for depositing on the surface of a plurality of particles aerosols within a fluid, a quasi-homogeneous amount of ions. The device includes a discharge corona conductive electrode, and a non-corona conductive receptor electrode. The receptor electrode has an open cellular foam structure and a pseudo planar active surface that faces the discharge electrode. The active surface of the receptor electrode has a multiplicity of substantially sharpened points.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a Divisional of prior U.S. patent application ser.No. 10/450,565, filed on Jun. 18, 2003, now U.S. Pat. No. 7,198,660entitled “ELECTROSTATIC DEVICE FOR IONIC AIR EMISSION,” which is theU.S. National Phase of PCT Application No. PCT/FR01/04019, filed Dec.17, 2001, both of which are hereby incorporated herein by reference.

TECHNICAL FIELD OF THE INVENTION

The present invention relates to the technical field of electrostaticair conditioning devices, and more specifically to devices forsubmitting a multitude of aerosol particles (such as dust, bio-aerosolsor specific molecules, . . . ) within a moving fluid to the action of anionic flow originating from corona discharge electrode, with a view:

-   -   on the one hand to homogenising the flow of ions relative to the        active plane face of a receptor electrode,    -   and, on the other hand, to depositing on the surface of this        multitude of aerosol particles (belonging to the same class of        diameter) a quasi-homogeneous quantity of ions.

The aim of this homogenisation of the deposit of ions on the surface ofthe particles can be to impart mechanical, physical, chemical, energeticconsequences of reduced intensity.

The invention relates to specifically to the technical field ofelectrostatic ionic emission and deposit devices of the type describedhereinafter, constituted by the combination between—on the one hand, adischarge corona conductive electrode, subjected to an electricdischarge potential, emitting an ion flow, —and on the other hand aporous non-corona conductive receptor electrode, subjected to adifferent potential, positioned relative to the corona electrode.

The invention further relates specifically to ionisation devices fittedwith a porous non-corona conductive receptor electrode, presenting apseudo-planar active face pierced with a multitude of fluid throughchannels. These channels traverse the receptor electrode and terminatein a multitude of orifices quasi-circular form, on an active face,according to the axis of flow of the fluid substantially perpendicularto the active face.

The invention also relates to ionisation devices which comprise meansfor pressurising fluid, ensuring movement of the fluid across thethickness of the electrode.

The invention finally relates to ionisation devices which are equippedwith an electric current comprising at least two metallic terminals,having a fairly high electric potential difference between them (of theorder of 5000V). At least two conductors are each connected—by one endto one of the two terminals de potential and/or to earth, —and by theother end respectively to a different terminal of the corona andreceptor electrodes, such that the two electrodes (corona and receptor)are subjected to sufficient electric potential difference to ensureionic emission in the discharge zone of the corona electrode.

The prior art knows the principle of electrostatic action devices byionic flow on aerosol particles, utilising the arrangements mentionedhereinabove. The devices belonging to this technical field are currentlymainly utilised for electrostatically filtering particles transported byan air flow.

But the prior art does not provide particular local geometricorganisation of the active face of the receptor electrode, the effect ofwhich is homogenisation of the flow of ions on the face of the receptorelectrode and/or homogenisation of the number of ions deposited on thesurface of the particles of the same size, carried along by the fluid.

On the contrary, the ionic electrostatic emission device according tothe invention comprises a particular local geometry of the active faceof its receptor electrode effectively establishing a surface flow ofions, originating from the corona electrode and in the direction of thepseudo-planar active face of the receptor electrode, having an ionicpunctual intensity exhibiting in the vicinity of the active face aspatial distribution of ionic intensity of increased homogeneity.

In addition, the invention renders quasi-homogeneous the number of ionsdeposited on the surface of the aerosol particles of a same size class.

PRIOR ART

The electrostatic device for homogenisation of ionic flow according tothe present invention has much wider applications than those of thefiltration field. Nevertheless, the closest prior art is essentiallyconstituted by electrostatic dust filters and also by certain devicesfor depositing ions on surfaces in the field of xerography. As aconsequence, analysis of the prior art hereinafter mainly targets thesetwo technical fields and more generally the various techniques of dustfiltration and xerography utilising a combination between a coronaelectrode emitting ions and a porous receptor electrode.

For medical, sanitary and air purity reasons, it is desirable to filterthe small particles of air and especially industrial dust, pollens,bacteria, virus, fungus, algae, and other dust fines . . . Beyondsystems operating by gravity (depositing of particles due to theirweight) and cyclone systems operating by centrifugal force (both ofwhich are used in certain specific industrial applications and end up asvery bulky systems), the two most current methods for ensuringdecontamination of dust in air consist of: —one barring the flow of airby means of an agent (mechanical filter), —and the other deviating andcapturing the dust by an electrostatic method (electrofilter). Anelectrostatic filter is based on the principle that particles, having acertain charge, are attracted by a collective electrode of the oppositecharge. This method has been used widely in industry since its inventionby F. G. Cottrell in 1910. Previously known means are used to give anelectrostatic charge to the particles, and, using an electrostaticfield, these charged particles are precipitated on a collective wall ora collector agent kept under electric voltage of opposite signs. Thereare mainly two classes of electrostatic filter structures: —singlestage, and double stage. There are also two variants of electrostaticprecipitation means: —that of electrodes charged under voltage generatedexternally by electric feed, —and that of electrostatic auto-charging,charged by air friction. The closest field to the invention is that ofdouble-stage electrofilters, whereof one stage is initial ionisation byexternal electric feed.

Double-stage electrofilters, also known as electrostatic precipitators,are highly complex, very costly and high efficacy. They comprise anelectric charge stage by corona effect of particles and a precipitationstage. During the electric charge stage the air passes over anionisation zone constituted generally by one or more high-voltage wires(corona electrodes) to generate an intense electrostatic field, in themidst of which the particles are charged electrically by ionisation.Then the air flow comprising the charged particles passes over a secondcollection stage. Two types of double-stage electrostatic filters aredistinguished, according to the structure of the collector stage of thecharged particles (—plate, —or filtering agent).

The particulars of the electrofilters close to the teaching of theinvention exclusively concern preliminary generation of ions and theirdeposit on the particles to be filtered (and more specifically commandof the homogeneity of the flow of ions) and not the efficacy of theprecipitation of dust.

A first major fault in ionisation systems according to the prior art isthat they do not have any means allowing a uniform quantity of ions tobe deposited on the treated aerosol particles. The consequence of thisis that a portion of the particles generally receives a sufficientquantity of ions (in fact, more than necessary) and another receives aquantity of ions too low to end up with an ulterior sufficient physicalresult. This reduces the efficacy of the electrofilters.

A second limitation to the prior art relative to ionic treatment ofparticles is that it does not provide an arrangement for depositing, onaerosol particles, a quasi-homogeneous quantity of ions (i^(q+)) and(i^(q−)) of opposite charges. This seems due to the fact that at firstit seems undesirable (even harmful) to deposit opposite charges on thesame aerosol particle. In effect, commonsense tends to point out thatthe ions of opposite charge are going to cancel each other out and thata reduced physical effect will thus be obtained. The inventors haveascertained that in particular industrial applications it was preferableto deposit on the external surface of aerosol particles (especially ofthe same diameter and/or same substance) quantities of ions both ofopposite charge and of a quasi-homogeneous quantity for each sign.

These two first types of faults of the prior art are mainly due to thefact that the flow of treated air has a transverse section generallyvastly superior to the efficacious transverse dimension of the dischargezones of corona electrodes used. Because of this, and in the absence ofcorrections connected to a particular local geometry of the receptorelectrode, the flow of ions reaching the aerosol particles decreasessharply in the transverse direction of the flow of fluid.

A third defect in the prior art is that when it aims to homogenise aflow of ions, this is done: —either in the event where there is nodisplacement of fluid (such as in xerographic systems), —or in the eventof geometry not permitting homogeneous ionic charging of aerosolparticles within substantial fluid rates.

The particular geometries of receptor electrodes utilised in the priorart in ionic generators acting on aerosol particles (especially inelectrofilters) do not generally intend to increase the ionichomogeneity, rather merely increase the electrostatic action between thereceptor electrode and previously charged particles, with a view toincreasing detection of dust. In addition, when particular geometries ofreceptor electrodes are used by the prior art, these relate to:—macroscopic global geometries of the system, —and not local surfacegeometries whose aim is ionic homogenisation, as is the case for theinvention.

U.S. Pat. No. 4,904,283 describes a filtration system constituted by asingle longilinear corona electrode placed at the centre of a cylinderconstituted by a filtering material and blocked at one end. The fluidcharged with particles is introduced at the other free end of thefiltering cylinder. The ionic flow in this cylindrical corona tubedecreases as an inverse function of the distance to the centre. Theionic deposit on the aerosol particles passing over it is thus veryinhomogeneous in the section of the tube. No particular local geometryof the surface of the receptor electrode (the interior of the cylinder)is provided and/or described for increasing the homogeneity of ionicdeposit. This device does not permit and furthermore does not claimhomogenisation of the deposit of ions on the aerosol particles.

U.S. Pat. No. 4,979,364 describes an electrofilter comprising upstream afirst ionising stage formed from a series of cylindrical dischargeelectrodes, perpendicular to the flow of fluid and a second filteringstage downstream constituted by a longitudinal beehive array subjectedto an electric or magnetic field. No local geometric arrangement of thesurface of the receptor electrode (beehive) is provided to increase thehomogeneity of the deposit of ions on the particles.

The aim of U.S. Pat. No. 4,910,637 is to homogenise the flow of ionstransmitted and the quantity of ozone emitted by a corona electrode in axerographic system. A ‘barrier’ is placed between the corona electrodeand the plane on which the ions are to be deposited. The proposedbarrier is constituted a) either by a dope material such as glass orceramic, b) or by glass or porous ceramic, c) or by a dispersion ofmetal or ceramic, d) or a conductive or semi-conductive material, e) orby a fibrous material having a catalysis function. The originality ofthis device does not therefore concern a particular surface geometry ofthe receptor electrode, but a particular choice of materials. Inaddition, this device is intended for deposit of ions on a planarsurface and not on aerosol particles. Finally, the system does notaffect any fluid in movement.

U.S. Pat. No. 4,871,515 describes an electrostatic filter comprising acorona electrode and a receptor electrode whose structure is fitted withconvolutions, pores or crevasses to increase its retention capacity. Nolocal geometric particularity of the surface of the receptor electrodeis provided to increase the homogeneity of the ionic flow and thedeposit of ions on the aerosol particles.

U.S. Pat. No. 4,597,781 describes an electrostatic precipitatorcomprising a central corona electrode generating negative ions,surrounded by a receptor electrode constituted by a cylindricalcollector tube. The receptor electrode has no particular local geometryof its active surface. The ionic flow in this cylindrical corona tubedecreases as an inverse function of the distance to the centre. Theionic deposit on the aerosol particles passing through it is thus veryinhomogeneous.

U.S. Pat. No. 4,898,105 describes an electrostatic filter constituted bya first stage of ionic charging constituted by corona electrodes placedtransversally to the flow of air and a second filtration stage (whichcan be assimilated into a receptor electrode) (decorated by a layer ofnon-conductive granules and a means for creating a transversalelectrostatic field across this layer. The system doe snot provide anyparticular local geometry of the surface of the layer of granules whoseeffect is homogenisation of the ionic flow originating from the firststage.

U.S. Pat. No. 4,313,739 describes a device for extracting a gas forpurifying a contaminant gas. The latter is constituted by an externaltube including a porous cylinder (which can be qualified as receptorelectrode) placed internally and a corona electrode placed in itscentre. A difference in potential is applied between the coronaelectrode and the cylinder. The gas to be purified is introduced at oneend of the cylinder. The system extracts a contaminant gas as a functionof its difference in ionisation potential vis-à-vis that of the gas tobe purified. The wall of the cylinder (receptor electrode) is eitherconstituted by a porous material, that is, one not having any particularsurface geometry, or is provided with pores traversing it anddistributed over its circumference. The active face of the receptorelectrode is not provided with any particular geometry (surrounding thepores) on its active internal face. This device does not allow and alsodoes not claim homogenisation of the deposit of ions on the aerosolparticles.

U.S. Pat. No. 4,066,526 describes an electrostatic filter constituted bya corona electrode and a receptor electrode. The receptor electrode hasno particular geometry on its active face. This device does not allowand also does not claim homogenisation of the deposit of ions on theaerosol particles.

U.S. Pat. No. 4,056,372 describes an electrostatic precipitatorconstituted by parallel metallic plates placed under alternatingelectric voltage and fitted with points at their ends. In a variant,corona electrodes of filaire type are placed upstream parallel andfacing the stack of plates. The flow of discharge ions is emittedtransversally between the filaire corona electrodes and parallel filairereceptor electrodes. This device does not describe a receptor. electrodeplaced transversally to the fluid path. The plates do not constitutereceptor electrodes facing the filaire corona electrodes. In addition,the surface of the plates is not provided with any quasi-circularorifice on their surface. This device does not allow and also does notclaim homogenisation of the deposit of ions on the aerosol particles.

U.S. Pat. No. 5,622,543 describes an air purifier including a planargeneratrix plate of anions (corona electrode) fitted with craters facinga planar receptor electrode provided with spaced holes. This devicecomprises no particular geometry on the surface of the receptorelectrode in view of the homogenisation of the deposit of ions on theaerosol particles.

U.S. Pat. No. 5,402,639 describes an electrostatic system for dedustinga gas, constituted by a hollow cylinder with a ceramic beehive wall,having orifices oriented radially, terminating from the interior towardsthe exterior of the cylinder and subjected to an internal electricalfield by means of external electrodes, and by a corona electrodesituated in its centre. Apart from its orifices, the cylinder has noparticular local surface geometry on its internal face facing the coronaelectrode which is suitable for enabling homogenisation of the depositof ions on the aerosol particles. In addition, due to its cylindricalstructure, and for the same reasons as described hereinabove, thissystem ensures an inhomogeneous deposit of ions on the particles.

U.S. Pat. No. 4,920,266 describes a xerographic system for depositingnegatives charges on a surface. This system comprises corona electrodesconstituted by a series of points disposed linearly side by side, facinga receptor electrode constituted by a metallic grille pierced byhexagonal orifices. Apart from its orifices, the receptor electrode doesnot comprise any particular surface geometry suitable for enablinghomogenisation of a flow of ions. In addition this device is intendedfor deposit of ions on a planar surface and not on aerosol particles.Finally, the system does not affect any fluid in movement.

U.S. Pat. No. 5,474,600, in the name of the applicants, describes abacteriological purification system, comprising an ionisation stageformed by a receptor electrode made of porous cellular metal and adischarge corona electrode facing the latter. No local geometriccharacteristic feature of the surface of the receptor electrode isprovided to increase the homogeneity of the ionic flow and/or deposit ofions on the aerosol particles.

SUMMARY OF THE INVENTION

In its general form the invention relates to an electrostatic ionicemission device homogenised for depositing on the surface of a multitudeof aerosol particles within a fluid, belonging to the same class ofdiameters, a quasi-homogeneous quantity of ions having the same charge.

An electrostatic ionic emission device according to the presentinvention is of the type described hereinbelow constituted by thecombination between—on the one hand, a conductive discharge coronaelectrode, subjected to an electric discharge potential and emitting aflow of ions, —and, on the other hand, a conductive non-corona receptorelectrode, subjected to a different electric reception potential. Thereceptor electrode has a pseudo-planar active face, situated oppositethe corona electrode and distant from its discharge zone. The free spaceseparating the active face of the receptor electrode from the coronaelectrode is free. A multitude of through channels of fluid traversesthe receptor electrode. They terminate via a multitude of quasi-circularorifices, on its active face, according to a so-called flow axis,substantially perpendicular to the active face. These channels ensure,in the vicinity of the active face, a flow of the fluid according toveins crossing the receptor electrode and are overall substantiallyparallel to the flow axis of fluid charged with aerosol particles. Thedevice further comprises means for pressurising a fluid, ensuringmovement of the fluid (especially across the thickness of the receptorelectrode), substantially in said flow axis and along the veins. Thedevice is equipped with a source of electric current, comprising atleast two metallic terminals having a sufficiently high electricpotential difference between them (of the order of 5000V) and at leasttwo conductors, each connected by an end to one of the potentialterminals and/or to earth, and by the other end, respectively to adifference of the corona electrodes and receptor, to subject these twoelectrodes to a difference in electric potential sufficient to ensureionic emission in the discharge zone of the corona electrode.

An electrostatic ionic emission device according to the presentinvention is remarkable by the following combination:

On the one hand, the multitude of through channels for fluid ispositioned across the receptor electrode in such a way that themultitude of their orifices is distributed quasi-uniformly on the activeface, in the two geometric directions of this face. And, on the otherhand, the pseudo-planar active face of the receptor electrode is coveredwith a plurality of zones sharpened to a point, sharp-edged and/orspiky. The latter emerge in relief from the active face. They presentlocally and at their end a minimum surface bend radius. These sharpzones are also distributed quasi-uniformly on this active face, in thetwo geometric directions of the surface and surround the orifices.

OBJECT

This particular local geometric combination of the receptor electrodeenables a surface flow of ions, originating from the corona electrodeand in the direction of the pseudo-planar active face of the receptorelectrode, having a punctual ionic intensity exhibiting at neighbouringpoints of the active face, a spatial distribution of ionic intensity ahomogeneity accrue, relative to the variation in spatial distancebetween—the point of projection corresponding to the active face of thereceptor electrode, —and the so-called zone of principal ionic actionsurrounding the geometric centre of the formed figure of the straightprojection of the discharge zone of the corona electrode on thepseudo-planar active surface.

This ionic homogeneity is established in a wide effective zonesurrounding the geometric centre. In such a way that in this largeefficacious zone a quasi-uniform quantity of ions is deposited on thesurface of the aerosol particles (of the same diameter class)transported by the fluid across the orifices.

DRAWINGS AND FIGURES

FIGS. 1 .a and 1 .b show diagrammatically, in section and inperspective, the state of the prior art in the form of an electrostaticionic emission device.

FIGS. 2 .a and 2 .b show diagrammatically, in section and inperspective, the closest prior art constituted by the electrostaticionic emission device equipping the bacteriological purification systemforming the object of U.S. Pat. No. 5,474,600.

FIGS. 3 .a and 3 .b show diagrammatically, in section and inperspective, the principal arrangements of an electrostatic ionicemission device for flow homogenisation and deposit of ions according tothe present invention.

FIGS. 4, 5 and 6 show in perspective three variants of an electrostaticionic emission device according to the present invention.

FIG. 7 shows in section and in perspective a bi-ionic emission systemaccording to the present invention traversed by a fluid charged withaerosol particles.

FIGS. 8 to 12 show the characteristic features of the constitution of aconductive material recommended by the invention to constitute theporous receptor electrode of an electrostatic ionic emission device.

FIG. 13 shows diagrammatically, in section, a variant of theelectrostatic ionic emission device recommended by the invention,whereof the receptor electrode is realised by means of the materialdescribed in FIGS. 8 to 12.

FIG. 14 shows diagrammatically, in section, another variant of thebi-ionic emission system recommended by the invention, whereof thereceptor electrodes are made of the material described in FIGS. 8 to 12.

FIG. 15 describes, in section, a variant of the bi-ionic emission systemaccording to the present invention with corona electrodes arranged inseries and in parallel.

FIGS. 16 and 17 show in section and in perspective, the action of abi-ionic emission system such as that in FIG. 14 on aerosol particles ina fluid in movement.

DETAILED DESCRIPTION OF THE USE OF THE INVENTION

FIGS. 1.a and 1.b show diagrammatically, in section (FIG. 1.a) and inperspective (FIG. 1.b), an electrostatic ionic emission device (11)according to the prior art. The electrostatic ionic emission device (11)according to the prior art comprises a corona discharge conductiveelectrode (EC), subjected to a negative electric discharge potential(VI), emitting a global flow (I) of negative ions (i^(q)). It alsocomprises a non-corona conductive receptor electrode (ER), subjected toa positive electric receptor potential (V2). The receptor electrode (ER)has an active face (SA) situated opposite the corona electrode (EC). Itis at a distance (di) from its negative ion (i^(q)) discharge zone (D).The space (H) separating the active face (SA) of the corona electrode(EC) is free. The receptor electrode (ER) is porous. It has a multitudeof through channels of the fluid (C1, C2, . . . , Cn), traversing thereceptor electrode (ER), and terminating in a multitude of orifices (O1,O2, . . . , On) on its active face (SA), according to a so-called flowaxis (xx′), substantially perpendicular to the active face (SA). Meansfor pressurising a fluid (not illustrated) ensures movement of the fluid(F) especially across the thickness (er) of the receptor electrode (ER),substantially in the flow axis (xx′).

In accordance with the prior art the surface geometry of the active face(SA) is random. No particular local geometric arrangement of the activeface (SA) is provided around the orifices (O1, . . . ) to homogenise theflow of negative ions (i^(q)).

The left portion of FIG. 1 .a illustrates the curve (12) of theintensity (J(Q)) of the-surface flow (Is(r)) of ions (i^(q)) in a plane(uu′) near the face (SA). These are ions (i^(q)) —originating from thecorona electrode (EC), —and in the direction of the pseudo-planar activeface (SA) of the receptor electrode (ER). The intensity (J(Q)) isillustrated according to the axis (xx′). The ionic punctual surfaceintensity (J(Q)) exhibits a highly inhomogeneous spatial distribution ofionic intensity (J(Q)) at points Q(r) near the active surface (SA). Itis noted that it decreases sharply when moving away from the centralflow axis (xx′) of the device (11), that is, with the increase inspatial distance (r), illustrated according to the axis (yy′), between:—the corresponding projection point (P(r)) of the active face (SA) ofthe receptor electrode (ER), —and the geometric centre (O) of theprojection point of the discharge zone (D) of the corona electrode (EC)on the pseudo-planar active surface (SA).

FIG. 1.a. illustrates the local intensity of the ionic flow Is(r)between the two electrodes (EC, ER) by clusters of ions (i^(q)). Thenumber of ions shown illustrates, on a radial, the intensity of the flowof ions in this direction. It is noted that when the point (Q(r)) andits projection (P(r)) move away from the geometric centre (O), thenumber of ions reaching the surface (SA) at (Q(r)), and by the samesurface flow Is(r), decreases considerably.

FIG. 1 .b illustrates in perspective the configuration of the device(11).

FIGS. 2 .a and 2 .b diagrammatically show, in section (FIG. 2 .a) and inperspective (FIG. 2 .b), a variant of the prior art in terms of an ionicemission electrostatic device (21) of the type such as described in U.S.patent application Ser. No. 5,474,600 in the name of the applicants. Itis noted that the discharge electrode (EC) is constituted by a coronapoint (22) placed at the end of a needle (23) perpendicular to theactive surface (SA). The corona point (22) is surrounded by a hollowmetallic tube (25) of minimum wall (26) thickness (ep), colinear to theaxis of point (x1,x′1) of the needle (23). The receptor electrode (ER)is made of porous cellular metal. The tube (25) and the electrode (ER)are connected and subjected to the same positive electric potential(V2). The discharge corona conductive electrode (EC) is subjected anegative discharge (Vi) electric potential. It emits a global flow (I)of negative ions (i^(q)) in its discharge zone (D). This flow of ionshas been illustrated by way of dotted lines of varying thickness,illustrating its intensity in different directions. In addition, thedifferent microscopic figures intervening in the process (especially theions and the particles) have been enlarged. It is noted that due to thepresence of the receptor electrode (ER), the flow of ions (i^(q)) in thedirection of the internal wall of the tube (25) is very weak (finelines). The curve (27) represents the variations of the ionic surfaceintensity J(r) in a plane (tt′) perpendicular to the axis (xx′) andcutting the tube (25) substantially in its centre. The ionic intensityIs(r) weakens rapidly inside the tube (25) and in its central part, as afunction of the distance (r) to the axis of the corona electrode (EC).It is easily understood that the variations of ionic intensity J(r) inthe plane (tt′) are at 1/r. Also illustrated on the curve (28) are thevariations of the ionic intensity J(r) in a plane (uu′) parallel to theactive surface (SA) of the receptor electrode (ER) in the region of thelatter. The ionic intensity J(r) also weakens rapidly as a function ofthe distance (r) to the axis (xx′) of the corona electrode (EC).

The active surface (SA) of the receptor electrode (ER) has no particularlocal geometry. As illustrated in FIG. 2 .b, this can be assimilated inapproximation to a holed plate (ER) provided with a multitude oforifices (O1, O2, . . . , On) on its active face (SA) and placed at anend of the tube (25).

FIG. 2 .a illustrates a flow (K) of fluid (F) which is made to penetrateinto the tube (25) via the receptor electrode (ER). The fluid (F) ischarged with a multitude of aerosol particles (p1). It can be consideredthat these particles (p1) are neutral before penetrating the device(21). After having crossed the receptor electrode (ER), the particlescome to face the flow of ions (i^(q)). For reasons mentioned hereinaboveof inhomogeneity of flow of ions (i^(q)), it is understood that theaerosol particles (p2) travelling close to the axis (xx′) receive asignificant quantity of negative ions (i^(q)). Four are illustrated. Onthe contrary, the particles (p3) transiting at a distance from the axis(xx′) receive much fewer negative ions (i^(q)). One is illustrated.

As a consequence, it is understood that this system (21) according tothe prior art does not permit either significantly homogenising a flowof ions (i^(q)) in the vicinity of a receptor electrode (ER), orsatisfactorily homogenising the flow of ions (i^(q)) deposited on theaerosol particles (p1, p2, p3, . . . ) traversing the system (21) fromone side to the other.

FIGS. 3 a and 3 b describe in section and in perspective, in their mostprimitive form, the improvements proposed by the invention to the ionicemission device (1). The general arrangements of this device (1)according to the present invention common to the devices (11, 21) of theprior art such as described in references 1 .a to 2 .b hereinabove, arereprised by the device (1) with the same references and are notrepeated.

The ionic emission electrostatic device (1) is intended to deposit onthe surface (sp) of a multitude of aerosol particles (p1) in a flow (K)of fluid (F), of the same diameter class (dp), a quasi-homogeneousquantity of ions (i^(q)) of charge (q). This electrostatic device (1) isa type constituted by the combination between a discharge coronaconductive electrode (EC), subjected to an electric discharge potential(V1), emitting a global flow (I) of ions (i^(q)) and a porous non-coronaconductive receptor electrode (ER), subjected to an electric receptorpotential (V2). The receptor electrode (ER) has a pseudo-planar activeface (SA), situated opposite the corona electrode (EC) and at a distance(di) from its discharge zone (D). The free space (H) separating itsactive face (SA) from the point (22) of the corona electrode (EC) isfree. A multitude of through channels of the fluid (C1, C2, . . . , Cn)traverses the receptor electrode (ER). They terminate via a multitude oforifices (O1, O2, . . . , On) quasi-circular in form on its active face(SA), according to the so-called flow axis (xx′), substantiallyperpendicular to the active face (SA). In the region of the active face(SA), they ensure flow of the fluid (F) according to the veins (notillustrated) traversing the receptor electrode (ER) and overallsubstantially parallel to said axis (xx′) of flow (K) of fluid (F).

The electrode (EC) with corona point (22) is surrounded by a hollow tube(25) of minimum wall (26) thickness (ep). The hollow tube (25) iscolinear to the point axis (x1, x′1) of the needle (23), according tothe axis (xx′) of the flow (K) of fluid (F) and situated opposite theactive face (SA) of the receptor electrode (ER). This hollow tube (25)encloses longitudinally the veins of fluid (F) relative to the activeface (SA) and around the needle (23). Preferably, the hollow tube (25)is constituted by an especially metallic conductive material (34). Thehollow tube (25) is carried at the same positive electric potential (V2)as the receptor electrode (ER) to effect electric protection vis-a-vis anegative potential (V1) of the corona electrode (EC).

FIG. 13 describes the additional specific details of the device (1)according to the present invention. Means (2) for pressurising the fluid(and especially a ventilator) ensures movement of the fluid (F),especially via the thickness (er) of the receptor electrode (ER),substantially in said flow axis (xx′), and along said veins (notillustrated). The device (1) is equipped with an electric current source(3) comprising at least two metallic terminals (B+, B−) in sufficientlyhigh electric potential difference between them (of the order of 5000V).Two conductors (4, 5) are each connected by an end (6, 7) to one of thepotential terminals (B+, B−) and/or to earth (8), and by the other end(9, 10) respectively to one difference of the corona (EC) and receptor(ER) electrodes. This in order to subject the two electrodes (EC, ER) toa difference of electric potential (V1)<>(V2) sufficient to ensure theionic emission of ions (iq) in the discharge zone (D).

It is noted with reference to FIG. 3 .b that the electrostatic ionicemission device (1) is equipped with a particular combination of thelocal surface geometry of the face (SA) of the receptor electrode (ER).On the one hand, its multitude of through channels (C1 C2, . . . , Cn)of fluid (F) are positioned across the receptor electrode (ER) such thatthe multitude of their orifices (O1, O2, . . . , Oi, . . . ,On) aredistributed quasi-uniformly on the active face (SA), in its twogeometric directions (yy′, zz′), and on the other hand the pseudo-planaractive face (SA) of the receptor electrode (ER) is covered with aplurality of zones sharpened into points (sharp-edged and/or spiky)(Ai). They emerge in relief from the active face (SA) and locallypresent a minimum surface bend radius (ra). They are distributedquasi-uniformly on this active face (SA), in its two geometricdirections (yy′, zz′). They enclose the orifices (O1, O2, . . . , Oi, .. . , On).

FIG. 3 .a illustrates the flow of ions (i^(q)) originating from thedischarge zone (D) of the corona electrode (EC) by means of dotted linesof varying thickness representing its ionic intensity (J(r)) indifferent directions. It is noted that due to the presence of theplurality of zones sharpened into points (sharp-edged and/or spiky) (Ai)emerging in relief from the active face (SA) and distributed uniformlyon the latter, the flow of ions (i^(q)) in the direction of the activeface (SA) of the receptor electrode has increased homogenisation (thedotted lines have similar width).

The curve (32), situated in the left part of FIG. 3 .a, illustrates thevariations of the ionic surface intensity J(r) in a plane (tt′)perpendicular to the axis (xx′) and cutting the tube (25) substantiallyin its centre. The ionic surface intensity J(r) weakens rapidly insidethe tube (25) as a function of the distance (r) to the axis of theelectrode (ER). In addition it is noted that the presence of the points(sharp-edged and/or spiky) (Ai) weakens the overall level of the flow ofions in the direction of the inner wall of the tube (25) relative towhat it is (see curve (27), FIG. 2 .a) in the absence of the sharp zones(Ai). There is a preponderant electrostatic action of the points (Ai)(sharp-edged and/or spiky) of the active face (SA) vis-a-vis that of theinner wall of the tube 25.

Also illustrated also on the curve (33) are the variations of the ionicsurface intensity J(r) in a plane (uu′) parallel to the active surface(SA) of the receptor electrode (ER), in the vicinity of the latter. Itis noted that, contrary to the curve (28), the ionic surface intensityJ(r) on the one hand weakens slightly as a function of the distance (r)to the axis (xx′) of the corona electrode (EC), and, on the other hand,at an overall level greater than that which is noted (such as on thecurve (32), FIG. 2 .a) when moving away from the receptor electrode(ER). A consequence of the geometric arrangement described hereinaboveis homogenisation of the ionic flow.

In fact, the ionic surface flow (Is(r)) of ions (i^(q)) originating fromthe corona electrode (EC) in the direction of the pseudo-planar activeface (SA) of the receptor electrode (ER), has a punctual ionic surfaceintensity J(Q(r)) presenting at the points Q(r) near the active face(SA) spatial distribution of ionic intensity J(r) at increasedhomogeneity, relative to the variation in spatial distance (r) betweenthe projection point (P(r)) corresponding to the active face (SA) of thereceptor electrode (ER), and the principal ionic action zone (A)enclosing the geometric centre (O) of the figure (G) of the straightprojection of the discharge zone (D) of the corona electrode (EC) on thepseudo-planar active face (SA). This is noted in a wide efficacious zone(S) enclosing the geometric centre (O) occupying the entire section ofthe tube (25). So much so that in this efficacious zone (S), and thus inthe entire section of the tube (25), a quasi-uniform quantity of ions(i^(q)) is deposited in the vicinity of the receptor electrode (ER) onthe surface (sp) of the aerosol particles (p1, . . . ) of the same classof diameter (dp) transported by the fluid (F) via the orifices (O1, O2,. . . , On). In addition, the influence of the inhomogeneity of theionic deposit in the central part (tt′) is very weak for the reasonscited hereinabove. So much so that the deposit of ions (i^(q)) on thesurface (sp) of the aerosol particles (p1) crossing from one side to theother in the system (1) is considerably homogenised relative to whatwould be obtained when passing via a device (11, 21) according to theprior art. The result of laboratory trials conducted by the applicantson a device (1) according to the present invention confirms thisphysical characteristic feature. The inventors have been able to confirmexperimentally by modifying the receptor electrodes of a device such asdescribed in U.S. patent application Ser. No. 5,474,600 according to theteaching of the invention and by measuring the physical results of thehomogenisation of the ionic deposit.

The invention can be utilised advantageously with several types ofcorona electrodes (EC).

Accordingly, according to the variant illustrated in FIGS. 3 .a and 3.b,the device (1) comprises the characteristic combination between: thepseudo-planar active face (SA) of the receptor electrode (ER) covered bya quasi-uniformly distributed plurality of sharpened emerging zones (Ai)surrounding orifices (O1, O2, . . . , On) also quasi-uniformlydistributed, and a discharge electrode (EC) constituted by a coronapoint (22) placed at the end of a needle (23). The latter is orientedaccording to a point axis (x1, x1′) perpendicular to the pseudo-planaractive face (SA), in the direction of the sharpened emerging zones (Ai),and positioned at a distance (di) opposite the active face (SA).

According to the variant illustrated in FIG. 6 the device (1) comprisesthe characteristic combination between: the pseudo-planar active face(SA) of its receptor electrode (ER) covered by a quasi-uniformlydistributed plurality of sharpened emerging zones (Ai) enclosing theorifices (O1, O2, . . . , On) also quasi-uniformly distributed, and adischarge electrode (EC) constituted by a conductive wire (41), orientedaccording to an axis (x2, x′2), substantially parallel to thepseudo-planar active face (SA). The conductive wire (41) issubstantially perpendicular to the sharpened emerging zones (Ai), andpositioned at a distance (di) opposite the active face (SA).

The invention recommends several types de geometry of sharpened emergingzones (Ai). According to the variant described in FIGS. 3 .a and 3 .bthe pseudo-planar active face (SA) of the receptor electrode (ER) iscovered by a quasi-uniformly distributed plurality of sharpened emergingzones (Ai) in the form of sharpened spiky points (42) uniformlydistributed, presenting locally a minimum surface bend radius (ra),surrounding the uniformly distributed orifices (O1, O2, . . . , On).These sharpened spiky points (42) point towards the exterior of theactive face (SA), according to a substantially perpendicular axis (xx′),in the direction of the discharge zone (D).

According to the variants described in FIGS. 4, 5 and 6, thepseudo-planar active face (SA) of the receptor electrode (ER) is coveredby a quasi-uniformly distributed plurality of craters (43) with sharpedges (Ai) closed in a pseudo circle (44). They have on their extremeedges a section of minimum bend radius (ra), surrounding the orifices(O1, O2, . . . , On), and terminate towards the exterior of the activeface (SA), according to a substantially perpendicular axis (xx′), in thedirection of the discharge zone (D).

FIG. 13 illustrates the variant embodiment recommended by the inventionof an electrostatic device (1) for homogenised ionic emission. Thereceptor electrode (ER) is constituted by a porous structure (51). Itszones sharpened into points (sharp-edged and/or spiky) (Ai) aredistributed quasi-uniformly on its active face (SA) and areinterconnected by means of this porous structure (51).

The receptor electrode (ER) is constituted by a porous structure (51)with alveolar mesh (52) constituted by an assembly in an array of fins(Ai, an) with longilinear portions (57). The plurality of its zonessharpened into points (sharp-edged and/or spiky) (Ai) distributedquasi-uniformly on the active face (SA) is delimited by sectioning ofthe structure of alveolar mesh (52) of the porous structure (51) to theright of the active face (SA).

The variant embodiment preferred by the invention of a receptorelectrode (ER) according to the invention appears in FIGS. 8 to 12. Thereceptor electrode (ER) supporting the pseudo-planar active face (SA) iscreated by means of a porous conductor block (55). This is constitutedby a pseudo-repetitive porous structure (51) with alveolar mesh (52)formed from a plurality of fins ( . . . , an, . . . ) with longilinearportions (57), constituted by an especially metallic conductive material(58).

As in FIGS. 8 and 9, the fins (an) have a fine transverse section (St),of a thickness (ea) much less than their longitudinal dimension (la).They comprise at least one lateral trailing edge (bn), elongated andtapered, (that is, of minimum local transverse bend radius (ra))oriented in the direction (xn, x′n) of the length of the fins (an).

As evident in FIG. 8, the fins ( . , . , a13, a14, a15, a16, . . . , an,. . . ) are physically and electrically interconnected by each of theirends (en1, en2) to constitute a three-dimensional conductive array(R′xyz). They are linked and grouped geometrically to form amultiplicity of elementary cells (c1, . . . , c16, c17, . . . ),communicating between one another to form the through channels (C1, C2,,Cn) of fluid (F). The internal fins (a13) on the porous block (55) aremainly common to several elementary cells ( . . . , c1, . . . , c17, . .. ). The majority of the linked fins (a13, a14, . . . ) belonging to thesame internal cell (c1) on the porous block (55) surround and jointangentially, by at least one of their lateral longitudinal faces (s1),a virtual elementary surface (62, 63) peculiar to and internal to eachelementary cell (c1, c17), of closed geometry, to contain a compact,empty, elementary cellular volume (59, 60). This means that itstransverse dimensions (dx1, dy1, dz1) are of the same order of magnitudein the three directions (x, y, z). The empty, elementary cellular volume(59) of the majority of the cells (c1) situated in the centre of theporous block (55) terminate opposite the empty, elementary volumes ( . .. , 60, . . . ) of neighbouring cells (c16, c17, . . . ) by at leastfour (and preferably twelve) craters (e16) across their elementarysurface (62). Each of the craters (e16) is surrounded by the lateraledge (b16) of fins ( . . . , a16 . . . ) belonging to its cell (c16) andcommon to the neighbouring cells ( . . . , c1, . . . ).

FIG. 10 schematically describes, on en enlarged scale, the surfaceaspect of the face (SA). With reference to FIGS. 10 and 13 it is notedthat the porous block (55) is cut pseudo-planar according to a so-calledactive face (SA), by sectioning a multitude of elementary cells (cA) ofthe end wall of the three-dimensional array (R′xyz), distributeduniformly on the active face (SA). A three dimensional array (R′xyz), amultitude of metallic nozzles (71), exhibiting sharp edges (72) andsubstantially circular in form compared to the active face (SA) isarranged to the right of each sectioned external cell (cA).

With reference to FIG. 8 it is noted that the cells (c16, c17, . . . )of the porous block (55) are positioned according to their distributionof greater density and have twelve neighbouring cells. They are piercedby twelve craters. The cells (c16, c17, . . . ) have a dodecahedrongeometry.

FIGS. 11 and 12 illustrate the interior of the porous block (55) inperspective.

The receptor electrode (ER) of the device (1) illustrated in FIG. 13 isconstituted by a substantially planar plate (64) presenting twosubstantially parallel pseudo-planar lateral faces:

-   -   a first so-called active face (SA) is situated opposite the        corona electrode (EC) and at a distance (di) from the discharge        zone (D), and a second face (S′A). It is noted that the divided        external cells (cA, c′A) are distributed on the surface of the        two lateral faces (SA, S′A). As has been described in FIG. 10,        they provided to the right of each divided external cell (cA,        c′A) a multitude of nozzles (72), exhibiting pointed edges (71)        of a substantially circular form compared to the corresponding        lateral support face (SA, S′A) of the receptor electrode (ER). A        multitude of through channels (Cn) of fluid (F) is provided via        the internal cells, and traverses the plate (64) constituting        the receptor electrode (ER). They connect each of the two faces        (SA) and (S′A) of the receptor electrode (ER). They terminate in        a multitude of orifices (On) on the first active face (SA),        according to a so-called flow axis (xx′), substantially        perpendicular to the first active face (SA). They also terminate        in a multitude of orifices (O′n) on the second face (S′A),        according to the axis (xx′) substantially perpendicular to the        second face (S′A). Due to the repetitive geometry of the array        (R′xyz), the multitude of through channels (Cn) of the fluid (F)        are constituted by and positioned across the receptor electrode        (ER) in such a way that the multitude of orifices (On) is        distributed quasi-uniformly on the first active face (SA), and        that the multitude of the orifices (O′n) is also distributed        quasi-uniformly on the second active face (S′A). The two        pseudo-planar active faces (SA, S′A) of the receptor electrode        (ER) are thus each covered in a plurality of zones sharpened        into points (sharp-edged and/or spiky) (Ai, A′i). They emerge in        relief, those (Ai) of the active face (SA) and the others (A′i)        of the active face (SA). They present locally a minimum surface        bend radius (ra). They are distributed quasi-uniformly on the        first active face (SA) and on the second face (S′A), and        surround said orifices (On) and (O′n).

The recommended manufacturing process for receptor electrodes (ER)according to the invention consists of first creating a primarydielectric or semi-conductor array. This primary array is geometricallyidentical to that of the array (R′xyz).

To make the primary array the process preferably consists, as in FIG. 8,of intersecting a multitude (preferably twelve) of closed materialsurfaces, having an envelope of minimum thickness (ea), arrangedsubstantially uniformly in the 3 directions (x, y, z), and made from afirst dielectric material (especially constituted by polyurethane).

Next, electrodepositing of a second metallic material (58), especiallynickel, is carried out on the primary array. In this way Athree-dimensional primary array having an external metallic surface isproduced.

The invention recommends producing the receptor electrode (ER) byelectrodepositing of nickel on a primary array of polyurethane.

The process first consists of making a plate as a primary porous arrayof fins (an) made of polyurethane. The primary array of polyurethane isthen given electrical conductivity by dipping it into a sensitivitysolution of the type: Sn Cl₁-25 g/l; HCl-40 ml/l. The primary array iskept in the solution for 10 minutes, then is washed in warm water for 10minutes. The primary array is then dipped for 5 minutes into a tankcontaining an activation solution of the type: Pd Cll-0.5 g/l HCl-10ml/l. It is then washed in warm water for 10 minutes.

A chemical layer of nickel is then applied to the primary array. Toachieve this the primary array is dipped into a solution of the type (enml/l):

NiS0₄•7H₂O 25 NaH₂PO₂•H₂O 25 NaP₂O₇•10H₂O 50 NH₄OH (28% sol) 23

The primary array is kept in the solution for 30 minutes. It is thenwashed in water for 10 minutes.

Electrodepositing of the nickel is then carried out. To do this, twonickel anodes are placed into an electrolysis vat. The primary array islaced between the two anodes in the vat which is then filled with asolution having a composition of the type (in g/l):

NiS0₄•7H₂0 250 1,4 butane diol 0.15 NiCl₂ 50 Phthalimide 0.12 H₃BO₃ 30pH 4.3-5.1

The anodes and the primary array are connected to different poles of adirect-current generator. (Anodes to the positive pole, primary array tothe negative pole). The intensity of the deposition current is regulatedat 0.5 A/dm² for 7 to 10 minutes. Ten successive deposition cycles arecarried out.

After metallic electrodepositing of the conductive material (58), theskeleton constituted by the underlying dielectric material is extractedby calorific or chemical action on the external metallic surface of theprimary array. This effectively produces a wholly metallic array(R′xyz). Preferably, the underlying polyurethane structure is withdrawnvia a thermal effect. To do this, the nickel-covered array is placed ina reducing atmosphere at a temperature of 1100° C. for 4 hours. Thearray (R′xyz) of the receptor electrode (ER) is then ready.

The receptor electrode (ER) of the device (1) in FIG. 13 is constitutedby a porous structure (51), with alveolar mesh (52) constituted by anarray assembly of fins (an) having longilinear portions (57). Theplurality of its zones sharpened into points (sharp-edged and/or spiky)(Ai) distributed quasi-uniformly on the first active face (SA) ismaterialised by dividing the structure of alveolar mesh (52) of theporous structure (51) of the array (R′xyz) to the right of the firstactive face (SA). Similarly, the plurality of its zones sharpened intopoints (sharp-edged and/or spiky) (A′i) distributed quasi-uniformly onthe second active face (S′A) is materialised by dividing the structureof alveolar mesh (52) of the porous structure (51) to the right of thesecond face (S′A).

FIG. 14 illustrates an bi-ionic emission electrostatic system (111)according to the invention for depositing for each sign aquasi-homogeneous quantity of ions (i^(q1)) and (i^(q2)) of oppositecharges on the surface (sp) of the same class of diameter (dp) of amultitude of aerosol particles (p1, p2, . . . ) in a fluid (F). Thisbi-ionic electrostatic system (111) is constituted characteristically bythe combination of two ionic emission electrostatic devices (101,102) ofinverse polarity chained in series, of the type (1) describedhereinabove. The electrostatic devices (101,102) are disposed in seriesaccording to a common axis (xx′) of flow (K) of fluid (F). It is notedthat the signs of polarity of the couples (V11, V12) and (V21, V22)corresponding, on the one hand, to the electric potential of theconductive corona electrodes (EC1, EC2), and on the other hand, to theelectric potential of the conductive non-corona receptor electrodes(ER1, ER2), of each of the two electrostatic devices (101, 102) areinverse. Means (2) for pressurising a fluid common to the two devices(1, 1′) ensures movement of the fluid (F) especially via the receptorelectrode (ER1) of the device (101) and (ER2) of the device (102),substantially in the common axis (xx′) of flow (K) of fluid (F).

The system (111) comprises three non-corona conductive receptorelectrodes (ER1, ER2, ER3) connected in series, and operated at varyingelectric potentials (V21, V22, V23). They were produced according to themanufacturing process described hereinabove. They have the geometryshown in FIGS. 8 to 12. They each have two substantially parallelpseudo-planar lateral faces: a first face (SA1, SA2, SA3), and a secondface (S′A1, S′A2, S′A3). A multitude of through channels for fluid (Cni)with (1<=i<=3) traverses each of the receptor electrodes (ERi) with(1<=i<=3) and connects each of the two faces (SAi) and (S′Ai) of eachreceptor electrode (ERi) with (i<=i<=3). They terminate in a multitudeof orifices (Oni), quasi-circular in shape, on the first active face(SA), along an axis (xx′) perpendicular to the first correspondingactive face (SAi), with (i<=i<=3). They also terminate in a multitude oforifices (O′ni) quasi-circular in shape, on the second face (S′Al),according to an axis (xx′) substantially perpendicular to the secondface (S′Ai), with (1<=i<=3).

It is recommended that the system comprise at least two conductivecorona discharge electrodes (EC1, EC2), subjected to a varying electricdischarge potential (V11, V12), emitting an overall flow (I1) of ions(i^(q1)), and (I2) of ions (i^(q2)) of opposite signs. The first coronaelectrode (EC1) is placed between the first couple of receptorelectrodes (ER1, ER2). Its discharge zone (D1) is located opposite theactive face (SA1) of one (ER1) of the two receptor electrodes (ER1, ER2)of the first pair. The second corona electrode (EC2) is placed betweenthe second couple of receptor electrodes (ER2, ER3). Its discharge zone(D2) is located opposite the active face (SA2) of one (ER2) of the tworeceptor electrodes (ER2, ER3) of the second pair.

Owing to the manufacturing method (described hereinabove) of theelectrodes (ER1, ER2, ER3), on the one hand the multitude of throughchannels (Cni) with (1<=i<=3) of each receptor electrode (ERi) ispositioned across the receptor electrode (ERi) such that the multitudeof orifices (Oni) is distributed quasi-uniformly in two directions (yy′,zz′) on the first active face (SAi). Similarly, the multitude oforifices (O′ni) is distributed quasi-uniformly on the second active face(S′Ai) in two directions (yy′, zz′).

It is recommended that the two pseudo-planar faces (SA2, S′A2) of thecentral receptor electrode (ER2) are each covered by a plurality ofzones sharpened into points (sharp-edged and/or spiky) (A2, A′2),emerging in relief, some (A2) from the first (SA2), and the other (A′2)from the second active face (SA′2). They locally present a minimumsurface bend radius (ra). They are distributed quasi-uniformly in thetwo directions (yy′, zz′). On the first face (SA2) they enclose thecorresponding orifices (Oni). On the second face (S′A2) they enclose thecorresponding orifices (O′ni). In fact, the three receptor electrodes ofthe system (111) illustrated in FIG. 14 are identical and have their 2faces structurally similar.

With reference to FIG. 15, this shows a variant of the bi-ionic emissionelectrostatic system (111) described in FIG. 14. The electrostaticsystem (131) has two stages (121,122) of ionic emission, organised inseries. Each stage (121,122) is constituted by the parallelcharacteristic combination of a plurality of ionic emissionelectrostatic devices (123,124, 125), (126, 127,128) of the type (1)described hereinabove. The electrostatic devices (123,124,125) of thesame stage (121) are disposed side by side transversely relative to theoverall flow axis (xx′) of fluid (F). The signs of polarity of thecouples (V1, V′1, V″1) and (V2, V′2, V″2) of the same stage (121),corresponding to the electric potential of the conductive coronaelectrodes, and to the electric potential of the non-corona conductivereceptor electrodes, or each of the two electrostatic devices(123,124,125), are similar. The receptor electrodes (ER1, ER′1, ER″1) ofthe electrostatic devices (123,124,125) are made by a common porousplate (64) constituted by an array (R′xyz) of fins (an) of the typedescribed hereinabove, situated transversely to the axis (xx′) of flow(F).

The overall functioning of the bi-ionic emission electrostatic system(111) described in FIG. 14 is described with reference to FIGS. 16 and17. A flow (K) of fluid (F) charged with particles (p1) is forced insidethe bi-ionic system (111) using pressurising means (2) (not illustratedin these figures). Due to the functional characteristic featuresdescribed hereinabove (common to the electrostatic devices (1) accordingto the present invention), inside the device (101) and owing to thecombined action of the corona electrode (EC1) and the receptor electrode(ER1) according to the invention, the overall flow of positive ions(i^(q1)) encountered in the through veins of flow (F), in passingthrough the device (101) according to the axis (xx′) of flow, isquasi-homogeneous in the entire section of its tube (25). As they passthrough the first device (101), the particles (p2) are thus charged by aquasi-homogeneous quantity of positive ions (i^(q1)). Four positive ions(i^(q1)) are illustrated on the particles (p2).

Similarly, within the device (102) and owing to the combined action ofthe corona electrode (EC2) and the receptor electrode (ER2) according tothe invention, the overall flow of negative ions (i^(q2)) found in thethrough veins of flow (F), when passing through the device (102)according to the flow axis (xx′), is quasi-homogeneous in the entiresection of its tube (25). When passing through the second device (102),the particles (p3) previously charged quasi-homogeneously with positiveions (i^(q1)) are also charged with a quasi-homogeneous quantity ofnegative ions (i^(q2)). Four positive ions (i^(q1)) and four negativeions (i^(q2)) are illustrated on the particles (p3).

Thus, as they exit from the bi-ionic system (111), the particles (p3)are covered with a homogeneous quantity of ions of opposite signs(i^(q1), i^(q2)).

The physical result obtained (illustrated by a star formation ofparticles (p³)) consists of freeing energy inside the particles (p3)having successively traversed the two electrostatic devices (101, 102)of the bi-ionic system (111). It is understood that, according toindustrial applications, this freeing of energy allows, by ionicrecombination, mechanical, physical, chemical, energetic consequences tobe inflicted on the particles (p3), of reduced intensity.

A characteristic feature of the bi-ionic system (111) according to theinvention is that the particles, at first charged with positive charges(^(q1)) from passing through the device (101), undergo, after passage ofthe electrode (ER2) and facing the corona electrode (EC2), thecombination of two effects inside the device (102):

-   -   a concentration effect of their trajectory in the direction of        the discharge zone of the corona electrode (EC2) of opposite        electric charge (negative),    -   and a blast effect of negative ions (i^(q2)) oriented according        to substantially colinear radials opposed to the movement of the        particles (p3), in the zone (H) separating the two electrodes        (EC2, ER2) of the device (102).

This appears in FIGS. 16 and 17 as indicated by arrow radialsoriginating from the corona electrode (EC2) of the device (102) in thedirection of the receptor electrode (ER2). This causes a “targeting”effect of the shocks between particles (p3) and negative ions (i^(q2))which, on the one hand, increases the efficacy (the quantity) of thedeposit of negative ions (i^(q2)) on the particles (p3), and, on theother hand, increases the homogeneity of the deposit of negative ions(i^(q2)) on the particles (p3), (due to the fact that the particles (p3)transit on radials subjected to an equivalent ionic intensity).

The inventors have ascertained experimentally that the combination ofthe bi-ionic system (111) according to the invention results inhomogeneity (expressed in terms of variation type) of deposits ofpositive ions (i^(q1)) and of negative ions (i^(q2)) on particles (p3),which they have measured to be about +31 10%. This was measured usingdevices (101,102) having a tube diameter of 5 cm, each equipped with adistant corona point of 2.5 cm of the receptor electrode and subjectedto a potential difference of +−5000 V. The testing was carried out onclasses of diameters of particles ranging from 0.01 micron to 3 microns.When the same testing was carried out with ionic emission devices ofequivalent size according to the prior art, the homogeneity of the ionicdeposit (expressed in terms of variant type) was around +−80% under thesame conditions.

ADVANTAGE OF THE INVENTION COMPARED TO THE PRIOR ART

It is ascertained that the devices (1) according to the presentinvention enable the flow of ions opposite the active face plane of areceptor electrode (ER) to be homogenised.

Likewise, it is determined that the devices (1) according to the presentinvention enable a multitude of aerosol particles (such as dust,bio-aerosols or specific molecules, . . . ) within a moving fluid, to besubjected to the action of an ionic flow originating from the coronadischarge electrode (EC), whereof the overall intensity inside any flowvein situated inside the tube (25) is quasi-homogeneous when passingthrough the tube.

It is also determined that the devices (1) according to the presentinvention enable a quasi-homogeneous quantity of ions (i^(q)) to bedeposited on the surface of this multitude of aerosol particles(belonging to the same class of diameters).

It is also ascertained that the devices (1) according to the inventionenable the efficacy of the flow of ions (i^(q)) to increase in thedirection of the electrode (ER) and thus in the direction of the flowveins, by reducing the radial less efficacious and inhomogeneous flow inthe direction of the wall (26) of the tube (25).

It is finally determined that bi-ionic systems (111) according to theinvention allow a homogeneous quantity of ions of opposite signs(i^(q1), i^(q2)) to be deposited on the surface of the particles.

INDUSTRIAL APPLICATIONS OF THE INVENTION

The invention finds industrial applications in numerous fields,especially physical, chemical, energetic, biological where it isappropriate to deposit a homogeneous quantity of ions on the aerosolparticles, with a view to imparting them with a reduced physical andquasi-uniform effect.

An immediate application concerns the field of electrostatic painting.Other applications are evident in the field of electrostatic filtration,such that all the particles passing through an electrostatic filter isquasi-uniformly precharged. The inventors have implemented the inventionin the field of biology to subject the external wall of micro-organismsto a reduced energetic action quasi-homogeneously modifying theirstructure and their internal configuration.

Although the above description contains numerous specifics, they do nothave to be considered as limiting the object of the invention, but asoffering illustrations of certain of the preferred modes ofimplementation of the invention.

The scope of the invention must be considered in relation to the claimshereinafter and their legal equivalents, rather than by the examplesmentioned hereinabove.

1. An ionic emission device comprising: a discharge corona electrode foremitting ions; and a porous metal receptor electrode having an opencelled metal foam structure and a pseudo planar active surface thatfaces the discharge electrode, the active surface having a multiplicityof substantially sharpened points, and wherein the receptor electrode isformed at least in part by electrodepositing metallic material on adielectric foam array skeleton.
 2. An ionic emission device as recitedin claim 1 wherein the dielectric foam away skeleton used in theformation of the receptor electrode is formed from a polyurethanematerial.
 3. An ionic emission device as recited in claim 1 wherein thesharpened points are quasi-uniformly distributed across the activesurface of the receptor electrode.
 4. An ionic emission device asrecited in claim 1 further comprising a power supply adapted to apply afirst potential to the receptor electrode and a second potential to thedischarge corona electrode, wherein the potential difference between thefirst and second potentials is at least approximately 5000 volts.
 5. Anionic emission device as recited in claim 1 wherein the discharge coronaelectrode includes a needle ionizing electrode having an axis that issubstantially perpendicular to the active surface of the receptorelectrode.
 6. An ionic emission device as recited in claim 1 furthercomprising an electrode chamber that is axially aligned with thedischarge corona electrode such that an axis of the electrode chamber issubstantially perpendicular to the active surface of the receptorelectrode.
 7. An ionic emission device as recited in claim 6 furthercomprising a power supply adapted to apply a first potential to theelectrode chamber and the receptor electrode and to apply a secondpotential to the discharge corona electrode.
 8. An ionic emission deviceas recited in claim 7 wherein the potential difference between the firstand second potentials is at least approximately 5000 volts.
 9. An ionicemission device comprising: a needle discharge electrode for emittingions; a metallic porous receptor electrode having an open celled metalfoam structure and a pseudo planar active surface that faces thedischarge electrode, the active surface having a multiplicity ofsubstantially sharpened points, wherein the receptor electrode is formedat least in part by electrodepositing metallic material on a dielectricfoam array skeleton; an electrode chamber that is axially aligned withthe discharge electrode such that an axis of the electrode chamber issubstantially perpendicular to the active surface of the receptorelectrode; and a power supply adapted to apply a first potential to thereceptor electrode and the electrode chamber and to apply a secondpotential to the discharge electrode, wherein the potential differencebetween the first and second potentials is at least approximately 5000volts.
 10. An ionic emission device as recited in claim 9 wherein thesharpened points are quasi-uniformly distributed across the activesurface of the receptor electrode.